Conventional hydropower typically incorporates a dam and a turbine driven by the hydraulic head. This type of dam based hydropower is efficient but may in many places be less suitable due to for example environmental concerns or that the terrain is inappropriate. Furthermore, this type of hydropower demands a fairly substantial initial investment and is consequently less profitable in places where the energy density of the river is low. Other hydropower solutions may consist of free turbines or turbines enclosed in pipes that utilises the water velocity in a manner similar to for example a wind mill. These types of low energy devices need to be fairly inexpensive in order to achieve an acceptable economic efficiency.
WO-2007/076866 discloses a hydropower device for generating electric power. The device comprises a pipe having an upstream portion and a downstream portion and being arranged to convey a flow of water. A valve member is provided on the pipe and adjustable between a closed position hindering the flow of water from exiting the pipe via the downstream portion or an open position permitting the flow of water to exit the pipe via the downstream portion. A cylinder member defines an inner space and has a passage between the inner space and the pipe upstream the downstream portion. The cylinder member extends away from the pipe along a centre axis and is configured to receive water from the flow of water at least when the first valve member is in the closed position. From the inner space water is conveyed to a turbine via a riser line.
U.S. Pat. No. 6,546,723 discloses another hydropower device for generating electric power. The device comprises a pipe having an upstream portion and a downstream portion and being arranged to convey a flow of water. A valve member provided at the upstream portion and adjustable between a closed position and an open position. A cylinder member defines an inner space and has a passage between the inner space and the pipe upstream the downstream portion. The cylinder extends away from the pipe and is configured to receive water from the flow of water at least when the first valve member is in the closed position.